Cyanobacterial polysaccharide : a huge tribute from the biological ancestor

Cyanobacteria are the oldest photosynthetic organisms which emitted a large amount of oxygen into the earth atmosphere, to make other creatures live on the ground. It is amazing that cyanobacteria are living still now to produce various metabolites which protect their own cell body. Especially extracellular polysaccharides (EPS) formed jelly matrixes surrounding the cell bodies to protect themselves from various biological and physical stressors for a pretty long time. Then cyanobacterial EPS must haveuseful functions inducing as an environmentally-benign resource for functional materials. However almost all of the cyanobacteria with jelly matrix could not be cultivated and then the materialization of their metabolites were difficult.Here we focused on Aphanothece sacrum which is a traditionally-cultivated cyanobacterium in a southern area in Japan, and which produced a large quantity of EPS to form big jelly matrixes. The novel, giant EPS with a molecular weight over 107 g/mol was extracted from the extracellular matrix of the cyanobacteria. Some unique properties resulting from the high molecular weight were found.Furthermore, we will show various unique polysaccharides derived from other cyanobacteria in the seminar.